Transcript Cell Cycle Notes

1. What process is this plant cell
undergoing?
2. Are the cells identical at the end of
the process?
The Life of a Cell
Cellular Transport and the Cell Cycle
Cell Reproduction
Cell Reproduction
Cell division is the process by which new
cells are produced from one cell.
Cell division results in two cells that are
identical to the original, parent cell.
New cells are constantly being produced.
The discovery of chromosomes
Chromosomes are structures which contain
DNA and become darkly colored when
stained
Chromosomes are the carriers of the genetic
material that is copied and passed from
generation to generation of cells.
Accurate transmission of chromosomes during
cell division is critical.
The structure of eukaryotic chromosomes
Centromere
Sister
chromatids
Supercoil within
chromosome
Chromosome
Continued coiling
within supercoil
Histone H1
Nucleosome
DNA
The Cell Cycle
The cell cycle is the sequence of growth and
division of a cell.
The majority of a
cell’s life is spent
in the growth
period known as
interphase.
Interphase
The Cell Cycle
Following interphase, a cell enters its period of
nuclear division called mitosis.
Following
mitosis, the
cytoplasm
divides,
separating the
two daughter
cells.
Mitosis
Interphase: A Busy Time
Interphase, the busiest phase of the cell cycle,
is divided into three parts.
Interphase
DNA synthesis
and replication
Rapid
growth and
metabolic
activity
Centrioles replicate;
cell prepares for
division
Interphase: A Busy Time
During the first part of interphase, the cell
grows and protein production is high.
Interphase
Rapid
growth
and
metabolic
activity
Interphase: A Busy Time
In the next part of interphase, the cell copies its
chromosomes.
Interphase
DNA synthesis
and replication
Interphase: A Busy Time
After the chromosomes have been duplicated, the
cell enters another shorter growth period in which
mitochondria and other organelles are
manufactured and cell parts needed for cell
division are assembled.
Interphase
Centrioles replicate;
cell prepares for
division
The Phases of Mitosis
The four phases of mitosis are prophase,
metaphase, anaphase, and telophase.
Prophase: The first phase of mitosis
Prophase: the chromatin coils to form visible
chromosomes.
Spindle fibers
Disappearing
nuclear envelope
Doubled
chromosome
Prophase: The first phase of mitosis
Sister chromatids are the two halves of the
doubled structure.
Sister
chromatids
Prophase: The first phase of mitosis
The centromere is the structure that holds two
sister chromatids together, which plays a role in
chromosome movement during mitosis.
Centromere
Metaphase: The second stage of mitosis
Metaphase: the chromosomes move to the
equator of the spindle.
Centromere
Sister
chromatids
Anaphase: The third phase of mitosis
Anaphase: the centromeres split and the sister
chromatids are pulled apart to opposite poles
of the cell.
Telophase: The fourth phase of mitosis
Telophase: two distinct daughter cells are
formed. The cells separate as the cell cycle
proceeds into the next interphase.
Nuclear
envelope
reappears
Two daughter cells are formed
Cytokinesis
Cytokinesis: following telophase, the cell’s
cytoplasm divides
Cytokinesis differs between plants and
animals.
Toward the end of telophase in animal cells,
the plasma membrane pinches in along the
equator.
Cytokinesis
Plant cells have a rigid cell wall, so the plasma
membrane does not pinch in.
A structure known as the cell plate is laid down
across the plant cell’s equator.
A cell membrane forms around each cell, and
new cell walls form on each side of the cell
plate until separation is complete.
Results of Mitosis
• When mitosis is complete, unicellular
organisms remain as single cells.
• Tissue: a group of cells that work together to
perform a specific function.
Results of Mitosis
• Organs: tissues organized in various
combinations to perform more complex roles
within the organism.
• Organ system: multiple organs that work
together
Biological Organization
• Organism: individual that exhibits all the
characteristics of life
Cell
Tissue
(muscle cell) (muscle tissue)
Organ
(stomach)
Organ System
(digestive tissue)
Organism
(Florida Panther)
Normal Control of the Cell Cycle
Proteins and enzymes control the
cell cycle
• The cell cycle is controlled by proteins called
cyclins and a set of enzymes that attach to
the cyclin and become activated.
• Occasionally, cells lose control of the cell
cycle.
Normal Control of the Cell Cycle
•
The uncontrolled dividing of cells can result
from
1. the failure to produce certain enzymes,
2. the overproduction of enzymes,
3. or the production of other enzymes at the
wrong time.
• Cancer is a malignant growth resulting from
uncontrolled cell division.
Normal Control of the Cell Cycle
• Enzyme production is directed by genes
located on the chromosomes.
• A gene is a segment of DNA that
controls the production of a protein.
Cancer: A mistake in the Cell Cycle
• Currently, scientists consider cancer to be a
result of changes in one or more of the genes
that produce substances that are involved in
controlling the cell cycle.
• Cancerous cells form masses of tissue called
tumors that deprive normal cells of nutrients.
Cancer: A mistake in the Cell Cycle
• In later stages, cancer cells enter the
circulatory system and spread throughout the
body, a process called metastasis, forming
new tumors that disrupt the function of
organs, organ systems, and ultimately, the
organism.
The causes of cancer
• The causes of cancer are difficult to pinpoint
because both genetic and environmental
factors are involved.
The causes of cancer
• Environmental factors,
such as cigarette smoke,
air and water pollution,
and exposure to
ultraviolet radiation
from the sun, are all
known to damage the
genes that control the
cell cycle.
The causes of cancer
• Cancer may also be caused by viral
infections that damage the genes.
Cancer prevention
• Physicians and dietary experts agree that diets
low in fat and high in fiber content can reduce
the risk of many kinds of cancer.
• Vitamins and minerals may also help prevent
cancer.
Cancer prevention
• In addition to
diet, other healthy
choices such as
daily exercise and
not using tobacco
also are known to
reduce the risk of
cancer.